1. Field of the Invention
The present invention relates generally to electromagnetic actuators, and particularly to such actuators as are embodied in an electromagnetic diaphragm or shutter having a flexible linkage that couples oppositely moving aperture blades together to coordinate their respective movements.
2. Description of the Prior Art
U.S. Pat. No. 4,333,722 discloses an electromagnetic actuator of the type having a current-conducting armature movable in a magnetic field, together with means for urging the armature toward a rest position. The armature has a planar coil thereon, and is movable in the plane of the coil. The armature is mounted for such movement by a flexure hinge, which not only biases the armature toward its initial position but also conducts current to and from the coil. The flexure hinge is described as a .lambda.-hinge that defines a virtual pivot point about which the armature rotates. An aperture blade is disposed at one end of the armature for movement thereby. A preferred embodiment of that actuator has two such armatures superposed in a magnetic field and separately mounted for opposing movements by respective .lambda.-hinges. The two armatures thus move in opposite directions when current flows through their coils, thereby changing the relative positions of their aperture blades. While the actuator there disclosed may prove satisfactory for some applications, a need still exists for an actuator of the same general type which is more efficient, more reliable, and more durable. In particular, an improved way of coordinating respective movements of cooperating armatures in such an actuator is needed to ensure consistently repeatable responses to successive actuations over an extended period of use.